Ink jet printing process

ABSTRACT

An ink jet printing process having the steps of: A) providing an ink jet printer that is responsive to digital data signals; B) loading the printer with ink jet recording elements having a support having thereon an image-receiving layer; C) loading the printer with an ink jet ink composition of water, humectant and a self-assembling colorant that is capable of spontaneously forming a nanoparticulate dispersion without any prior physical attrition or surface modification, the colorant having the formula: (A) m -Q-(Z) n  wherein: Q represents a chromophore; each A independently represents an organic or inorganic group capable of hydrogen bonding or other non-covalent bonding; each Z independently represents an organic or inorganic group capable of electrostatic bonding; and m and n each independently represents an integer from 0 to 10; with the proviso that n+m is at least 1; and with the further proviso that at least about 50 wt. % of the colorant is present in the composition as particles; and D) printing on the image-receiving layer using the ink jet ink in response to the digital data signals.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] Reference is made to commonly assigned, co-pending U.S. patentapplications:

[0002] Ser. No. ______ by Andrievsky et al., filed concurrently herewith(Docket 84969) entitled “Ink Jet Ink Composition”;

[0003] Ser. No. ______ by Andrievsky et al., filed concurrently herewith(Docket 84190) entitled “Ink Jet Ink Composition”; and

[0004] Ser. No. ______ by Andrievsky et al., filed concurrently herewith(Docket 84968) entitled “Ink Jet Printing Process”.

FIELD OF THE INVENTION

[0005] This invention relates to an ink jet printing process using anink jet ink composition for improving the ozone and light stability ofan ink jet image.

BACKGROUND OF THE INVENTION

[0006] Ink jet printing is a non-impact method for producing images bythe deposition of ink droplets in a pixel-by-pixel manner to animage-recording element in response to digital signals. There arevarious methods that may be utilized to control the deposition of inkdroplets on the image-recording element to yield the desired image. Inone process, known as continuous ink jet, a continuous stream ofdroplets is charged and deflected in an imagewise manner onto thesurface of the image-recording element, while unimaged droplets arecaught and returned to an ink sump. In another process, known asdrop-on-demand ink jet, individual ink droplets are projected as neededonto the image-recording element to form the desired image. Commonmethods of controlling the projection of ink droplets in drop-on-demandprinting include piezoelectric transducers and thermal bubble formation.Ink jet printers have found broad applications across markets rangingfrom industrial labeling to short run printing to desktop document andpictorial imaging.

[0007] The inks used in the various ink jet printers can be classifiedas either dye-based or pigment-based. A dye is a colorant that ismolecularly dispersed or solvated by a carrier medium. The carriermedium can be a liquid or a solid at room temperature. A commonly usedcarrier medium is water or a mixture of water and organic co-solvents.Each individual dye molecule is surrounded by molecules of the carriermedium. In dye-based inks, no particles are observable under themicroscope. Although there have been many recent advances in the art ofdye-based ink jet inks, such inks still suffer from deficiencies such aslow optical densities on plain paper and poor light-fastness. When wateris used as the carrier medium, such inks also generally suffer from poorwater-fastness.

[0008] A pigment is a colorant that is insoluble in the carrier medium,but is dispersed or suspended in the form of small particles, oftenstabilized against flocculation and settling by the use of dispersingagents. Many such compounds are known and are commercially used. ColorIndex International (publication by the Society of Dyers and Colorists,1997) lists various classes of pigments. It is common practice toproduce pigment compositions in the form of finely divided dispersions,which may be generated by well-known methods such as ball milling. Inorder to obtain the optimum dispersion properties it is common to havepresent at least one dispersant, and the choice of dispersant isimportant for achieving acceptable pigment dispersion properties. Thepurpose of the dispersant is to stabilize the particles and to preventgrowth by aggregation and flocculation. However, merely adsorbing adispersant to the pigment surface may lead to competition for suchdispersant from solvents and humectants used in the ink formulation andmay lead to desorption. In general, such systems may also suffer from adependence on the concentration of the pigment, the type of humectantsused, and the temperature and pH of the formulation containing thepigment. Therefore, it is often difficult to identify an acceptabledispersant which provides the needed ink stability and is compatiblewith other components in the ink formulation.

[0009] Images obtained from pigment-based inks generally have betterlight-fastness and ozone-fastness than that of the images obtained fromdye-based inks. It is especially true when these are used with arecording element containing a porous image-receiving layer. However,pigment based inks have not received a wide degree of acceptance in inkjet ink systems, because of problems associated with the preparation,performance and reliability of the composition, such as dispersability,print properties, dispersion stability, latency, smear, and gloss.

[0010] When a pigment-based ink is formulated, a dispersant is normallyused along with a milling or physical grinding step. Alternatively,after milling, the pigment surface may be chemically modified to renderthe particles dispersible in an aqueous formulation. However, there is aproblem with these techniques in that they take time and are expensive.It would be desirable to find alternative colorants having the imagepermanence of pigments but which do not require milling.

[0011] U.S. Pat. No. 5,922,118, EPA 0904327, and WO9747699 disclosesurface-modified pigments, wherein such surface modification comprisesionic or ionizable groups for improvement of pigment dispersability.However, these pigments still require a milling step.

[0012] EP 1146094 describes pigment compositions for paints and inksconsisting of mixtures of salts of quinacridone monosulfonic acids andquinacridone pigments. The quinacridone monosulfonic acid derivatives ofthis reference are not water-soluble and the pigment compositionsrequire mechanical milling to achieve acceptable dispersions.

[0013] U.S. Pat. Nos. 6,066,203 and 5,368,641 describe mono- andbis-sulfamoyl (—SO₂NRR′) derivatives (respectively) of quinacridones foruse in formulating quinacridone pigment dispersions similar to thosedescribed in EP1146094 above.

[0014] It is an object of the invention to provide an ink jet printingprocess using an ink jet ink composition that employs self-dispersedparticles that do not require milling or grinding and do not require theuse of a dispersant.

SUMMARY OF THE INVENTION

[0015] This and other objects are achieved in accordance with thepresent invention which comprises an ink jet printing process comprisingthe steps of:

[0016] A) providing an ink jet printer that is responsive to digitaldata signals;

[0017] B) loading the printer with ink jet recording elements comprisinga support having thereon an image-receiving layer;

[0018] C) loading the printer with an ink jet ink composition comprisingwater, humectant and a self-assembling colorant that is capable ofspontaneously forming a nanoparticulate dispersion without any priorphysical attrition or surface modification, the colorant having theformula:

(A)_(m)-Q-(Z)_(n)

[0019] wherein:

[0020] Q represents a chromophore;

[0021] each A independently represents an organic or inorganic groupcapable of hydrogen bonding or other non-covalent bonding;

[0022] each Z independently represents an organic or inorganic groupcapable of electrostatic bonding; and

[0023] m and n each independently represents an integer from 0 to 10;

[0024] with the proviso that n+m is at least 1; and with the furtherproviso that at least about 50 wt. % of the colorant is present in thecomposition as particles; and

[0025] D) printing on the image-receiving layer using the ink jet ink inresponse to the digital data signals.

[0026] It was found that the ozone and light stability of an ink jetimage was improved when printing using the composition described herein.

DETAILED DESCRIPTION OF THE INVENTION

[0027] The chromophore (O) of the colorant of the invention may bechosen from any of the commonly used dye and pigment chromophoricclasses. In particular, those classes that are capable ofself-assembling through strong intermolecular non-covalent associativeforces such as electrostatic bonding, van der Waals interactions,hydrogen bonding, hydrophobic interactions, dipole-dipole interactions,dipole-induced dipole interactions, London dispersion forces, cation -πinteractions, etc. are especially preferred. Self-assembly is a processof reversible, spontaneous formation of polymolecular aggregates fromself-complementary and mutually-complimentary components. Examples ofsuch classes include the following chromophores: metal and metal-freephthalocyanines; anthraquinones; naphthoquinones; quinacridones;quinophthalones; indigos; thioindigos; perylenes; dioxazines;1,4-diketopyrrolopyrroles; anthrapyridines; anthrapyrimidines;anthanthrones; flavanthrones; indanthrones; isoindolines;isoindolinones; perinones; pyranthrones; porphyrins and azo compounds.

[0028] In a preferred embodiment of the invention, the colorant issubstituted with a mixture of organic or inorganic water-solubilizinggroup or groups capable of electrostatic bonding (Z) and/or organic orinorganic hydrophilic non-ionic groups capable of hydrogen bonding orother non-covalent bonding (A) in such a ratio that the colorantspontaneously forms a nanoparticulate dispersion in an aqueous carrierliquid without prior attritive milling or other high-energy dispersingtechniques or prior surface modification. The ionic water-solubilizinggroups (Z) may be anionic, such as sulfonate, sulfinate, phosphonate orcarboxylate; or cationic such as ammonium, substituted ammonium,pyridinium, amidinium or guanidinium. The non-ionic, hydrophilic groups(A) may be hydroxy groups, sugar residues, polyoxyalkylene groups suchas poly(ethyleneoxide), sulfamoyl or carbamoyl groups and their mono-and di-substituted derivatives, heterocyclic moieties such astetrahydrofuran, imidazole and the like, or alkylsulfonyl groups.

[0029] In a particularly preferred embodiment, the ionicwater-solubilizing groups (Z) are sulfonate groups and non-ionichydrophilic groups (A) are mono- or di-substituted sulfamoyl groups.

[0030] Particularly preferred colorant classes are the phthalocyaninesand quinacridones with the following formulas:

[0031] Phthalocyanine—

MPc(SO₃X)_(a)(SO₂NRR′)_(b)

[0032] wherein:

[0033] M represents a metal;

[0034] Pc represents a phthalocyanine nucleus;

[0035] X represents hydrogen, alkali metal or an organic cation, such asNa, Li, or ammonium;

[0036] a is from 0 to 3;

[0037] R represents a substituted or unsubstituted alkyl group havingfrom 1 to about 15 carbon atoms, a substituted or unsubstituted arylgroup, or a substituted or unsubstituted heterocyclic group;

[0038] R′ represents R or hydrogen;

[0039] with the proviso that a+b is an average of from 2 to 4;

[0040] In an especially preferred embodiment of the invention, R in theabove formula represents a substituted or unsubstituted alkyl grouphaving from 1 to about 15 carbon atoms containing a hydroxy group, asubstituted or unsubstituted aryl group containing a hydroxy group or asubstituted or unsubstituted heterocyclic group containing a hydroxygroup. In another preferred embodiment, M in the above formularepresents copper, nickel, aluminum, zinc, iron, or cobalt. In anotherpreferred embodiment, R in the above formula represents CH₂CH₂OH. Inanother preferred embodiment, M represents Cu or Ni and R is CH₂CH₂OH.

[0041] Quinacridone—

[0042] wherein:

[0043] each R₁ independently represents an alkyl group of from 1 toabout 6 carbons; an alkoxy group of from 1 to about 6 carbons; analkoxycarbonyl group of from 1 to about 6 carbons; halogen; cyano;nitro; carbamoyl; an alkylcarbamoyl group of from 1 to about 6 carbons;or a dialkylcarbamoyl group of from 1 to about 6 carbons;

[0044] R₂ and R₃ independently represent H or an alkyl group of from 1to about 6 carbons, optionally substituted with one or more groupschosen from hydroxy, amino, dialkylamino, alkoxy, halogen, nitro, cyano,alkoxycarbonyl and acyloxy.

[0045] R₂ and R₃ may also be combined to form a 5- to 7-memberedheterocyclic ring;

[0046] Y⁺ represents an alkali metal, ammonium, alkylammonium,dialkylammonium, trialkylammonium, tetralkylammonium, pyridinium or asubstituted pyridinium; and

[0047] x represents an integer from 0 to 4;

[0048] In another preferred embodiment, at least about 70 wt. %, morepreferably 80 wt. % of the colorant is present in the composition asparticles. In another preferred embodiment, the particles are less thanabout 0.3 μm, more preferably less than about 0.1 μm in size.

[0049] In another preferred embodiment of the invention, the metallized,phthalocyanine colorants that may be used include the following: TABLE1a

Colorant M Z₁ Z₂ Z₃ Z₄ Substitution 1 Cu DA DA DA DA 4,4′,4″,4′′′ 2 CuSX DA DA DA 4,4′,4″,4′′′ 3 Cu SX SX DA DA 4,4′,4″,4′′′ 4 Cu SX SX SX DA4,4′,4″,4′′′ 5 Cu DA DA DA DA random 6 Cu SX DA DA DA random 7 Cu SX SXDA DA random 8 Cu SX SX SX DA random 9 Cu DA DA DA N/S random 10 Cu SXDA DA N/S random 11 Cu SX SX DA N/S random 12 Cu DA DA N/S N/S random 13Cu SX DA N/S N/S random 14 Ni DA DA DA DA 4,4′,4″,4′′′ 15 Ni SX DA DA DA4,4′,4″,4′′′ 16 Ni SX SX DA DA 4,4′,4″,4′′′ 17 Ni SX SX SX DA4,4′,4″,4′′′ 18 Cu EA EA EA EA 4,4′,4″,4′′′ 19 Cu SEA EA EA EA random 20Ni SEA SEA EA EA 4,4′,4″,4′′′ 21 Ni SEA SEA SEA EA random 22 Cu EA EA EADA 4,4′,4″,4′′′ 23 Cu SEA EA EA DA random 24 Ni SEA SEA EA EA4,4′,4″,4′′′ 25 Co SEA SEA SEA EA random 26 Cu DA DA EA N/S random 27 CuSX DA EA N/S random 28 Cu SX SEA DA N/S random 29 Cu DA EA N/S N/Srandom 30 Ni SX DA N/S N/S random 31 Cu SPY SPY SPY SNa random 32 Cu SPYSPY SPH SNa random 33 Ni SPY SPY SNa SNa random 34 Ni SPY SPY SPH SNarandom 35 Cu SPY SPY SPH SNa 4,4′,4″,4′′′ 36 Ni SPY SPY SPH SNa4,4′,4″,4′′′

[0050]

[0051] SNa=SO₃ ⁻Na⁺

[0052] N/S=no substituent.

[0053] Electrophilic substitution or construction of the phthalocyaninenucleus leads to a mixture of products. In each aromatic ring, as shownin the generalized structure below, substitution may occur at one of the4 or 4a positions, which are equivalent, or at one of the 3 or 3apositions, which are equivalent.

[0054] Numbering of position of substitution

[0055] The descriptors in Table 1a, ‘Substitution’ column have thefollowing meanings: 4, 4′, 4″, 4′″: substitution occurred to give onesubstituent in each aromatic ring at a 4 or 4a position; random:wheresubstitution occurred, the substituent is present in one of the 3, 4, 4aor 3a positions in each aromatic ring.

[0056] Colorant A Composition is predominantly a mixture of Colorants1-4 and includes positional isomers of Colorants 1-4;

[0057] Colorant B Composition is predominantly a mixture of Colorants5-13 and includes positional isomers of Colorants 5-13;

[0058] Colorant C Composition is predominantly a mixture of Colorants14-17 and includes positional isomers of Colorants 14-17.

[0059] In another preferred embodiment of the invention, thequinacridone colorants that may be used include the following: TABLE 1b

Col- or- ant M⁺ R₁ R₂ 37 H₂N⁺(C₂H₄OH)₂ C₂H₄OH C₂H₄OH 38 H₃N⁺C₂H₄OH HC₂H₄OH 39 Na⁺ CH₃ C₂H₄OH 40 N⁺(CH₃)₄ H CH₂CH(OH)CH₂OH 41 Na⁺ CH₃ CH₃ 42Na⁺ H C₃H₆N(CH₃)₂ 43 Na⁺ C₂H₄CO₂CH₃ C₂H₄CO₂CH₃ 44 Na⁺ HCH₂[CH(OH)]₄CH₂OH 45 NH₄ ⁺ H H 46 Na⁺ C₂H₄CONHCH₃ C₂H₄CONHCH₃ 47

—C₂H₄OC₂H₄— 48

—C₄H₈— 49

50

[0060] Colorant D Composition is predominantly Colorant 37

[0061] The colorants described above may be employed in any amounteffective for the intended purpose. In general, good results have beenobtained when the colorant is present in an amount of from about 0.2 toabout 10 wt. %, the humectant is present in an amount of from about 5 toabout 70 wt. %, and the balance is water. A dye may also be added to theink jet ink composition if desired.

[0062] The support for the ink jet recording element used in theinvention can be any of those usually used for ink jet receivers, suchas paper, resin-coated paper, plastics such as a polyester-type resinsuch as poly(ethylene terephthalate), polycarbonate resins, polysulfoneresins, methacrylic resins, cellophane, acetate plastics, cellulosediacetate, cellulose triacetate, vinyl chloride resins, poly(ethylenenaphthalate), polyester diacetate, various glass materials, andmicroporous materials such as microvoided polyester described incopending U.S. Ser. No. 09/656,129, filed Aug. 29, 2000, polyethylenepolymer-containing material sold by PPG Industries, Inc., Pittsburgh,Pa. under the trade name of Teslin®, Tyvek® synthetic paper (DuPontCorp.), and OPPalyte® films (Mobil Chemical Co.) and other compositefilms listed in U.S. Pat. No. 5,244,861. The thickness of the supportemployed in the invention can be, for example, from about 12 to about500 μm, preferably from about 75 to about 300 μm.

[0063] Antioxidants, antistatic agents, plasticizers and other knownadditives may be incorporated into the support, if desired. In apreferred embodiment, paper is employed.

[0064] In a preferred embodiment of the invention, the ink-receivinglayer is porous and contains inorganic particles such as silica,alumina, titanium dioxide, clay, calcium carbonate, barium sulfate, orzinc oxide. In another preferred embodiment, the porous ink-receivinglayer comprises from about 30 wt. % to about 95 wt. % inorganicparticles and from about 5 wt. % to about 70 wt. % polymeric binder,such as gelatin, poly(vinyl alcohol), poly(vinyl pyrrolidinone) orpoly(vinyl acetate). The porous ink-receiving layer can also containorganic beads or polymeric micro-porous structures without inorganicfiller particles as shown in U.S. Pat. Nos. 5,374,475 and 4,954,395, thedisclosures of which are hereby incorporated by reference.

[0065] Examples of binders which may be used in the image-receivinglayer include polyvinyl alcohol, polyvinyl pyrrolidone, poly(ethyloxazoline), non-deionized or deionized Type IV bone gelatin, acidprocessed ossein gelatin or pig skin gelatin. The hydrophilic polymermay be present in an amount of from about 0.4 to about 30 g/m²,preferably from about 1 to about 16 g/m².

[0066] The pH of the aqueous ink compositions employed in the inventionmay be adjusted by the addition of organic or inorganic acids or bases.Useful inks may have a preferred pH of from about 2 to 9, depending uponthe type of dye being used. Typical inorganic acids includehydrochloric, phosphoric and sulfuric acids. Typical organic acidsinclude methanesulfonic, acetic and lactic acids. Typical inorganicbases include alkali metal hydroxides and carbonates. Typical organicbases include ammonia, triethanolamine and tetramethylethylenediamine.

[0067] One or more humectants are employed in the ink jet compositionemployed in the invention to help prevent the ink from drying out orcrusting in the orifices of the printhead. Examples of humectants whichcan be used include polyhydric alcohols, such as ethylene glycol,diethylene glycol, triethylene glycol, propylene glycol, tetraethyleneglycol, polyethylene glycol, glycerol, 2-methyl-2,4-pentanediol1,2,6-hexanetriol and thioglycol; lower alkyl mono- or di-ethers derivedfrom alkylene glycols, such as ethylene glycol mono-methyl or mono-ethylether, diethylene glycol mono-methyl or mono-ethyl ether, propyleneglycol mono-methyl or mono-ethyl ether, triethylene glycol mono-methylor mono-ethyl ether, diethylene glycol di-methyl or di-ethyl ether, anddiethylene glycol monobutylether; nitrogen-containing cyclic compounds,such as pyrrolidone, N-methyl-2-pyrrolidone, and1,3-dimethyl-2-imidazolidinone; and sulfur-containing compounds such asdimethyl sulfoxide and tetramethylene sulfone. Preferred humectants forthe composition of the invention are diethylene glycol, glycerol, anddiethylene glycol monobutylether.

[0068] Water-miscible organic solvents may also be added to the aqueousink employed in the invention to help the ink penetrate the receivingsubstrate, especially when the substrate is a highly sized paper.Examples of such solvents include alcohols, such as methyl alcohol,ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,sec-butyl alcohol, t-butyl alcohol, iso-butyl alcohol, furfuryl alcohol,and tetrahydrofurfuryl alcohol; ketones or ketoalcohols such as acetone,methyl ethyl ketone and diacetone alcohol; ethers, such astetrahydrofuran and dioxane; and esters, such as, ethyl lactate,ethylene carbonate and propylene carbonate.

[0069] Surfactants may be added to adjust the surface tension of the inkto an appropriate level. The surfactants may be anionic, cationic,amphoteric or nonionic. A preferred surfactant for the ink compositionof the present invention is Surfynol® 465 (Air Products) at a finalconcentration of 0.1% to 1.0%.

[0070] A biocide may be added to the composition employed in theinvention to suppress the growth of micro-organisms such as molds,fungi, etc. in aqueous inks. A preferred biocide for the ink compositionemployed in the present invention is Proxel® (GXL (Zeneca SpecialtiesCo.) at a final concentration of 0.05-0.5 wt. %.

[0071] A typical ink composition employed in the invention may comprise,for example, the following substituents by weight: colorant (0.2-5%),water (20-95%), humectant (5-70%), water miscible co-solvents (2-20%),surfactant (0.1-10%), biocide (0.05-5%) and pH control agents (0.1-10%).

[0072] Additional additives which may optionally be present in the inkjet ink composition employed in the invention include thickeners,conductivity enhancing agents, anti-kogation agents, drying agents, anddefoamers.

[0073] The image-recording layer used in the process of the presentinvention can also contain various known additives, including mattingagents such as titanium dioxide, zinc oxide, silica and polymeric beadssuch as crosslinked poly(methyl methacrylate) or polystyrene beads forthe purposes of contributing to the non-blocking characteristics and tocontrol the smudge resistance thereof; surfactants such as non-ionic,hydrocarbon or fluorocarbon surfactants or cationic surfactants, such asquaternary ammonium salts; fluorescent dyes; pH controllers;anti-foaming agents; lubricants; preservatives; viscosity modifiers;dye-fixing agents; waterproofing agents; dispersing agents; UV-absorbingagents; mildew-proofing agents; mordants; antistatic agents,anti-oxidants, optical brighteners, and the like. A hardener may also beadded to the ink-receiving layer if desired.

[0074] In order to improve the adhesion of the image-recording layer tothe support, the surface of the support may be subjected to a treatmentsuch as a corona-discharge-treatment prior to applying theimage-recording layer.

[0075] In addition, a subbing layer, such as a layer formed from ahalogenated phenol or a partially hydrolyzed vinyl chloride-vinylacetate copolymer can be applied to the surface of the support toincrease adhesion of the image recording layer. If a subbing layer isused, it should have a thickness (i.e., a dry coat thickness) of lessthan about 2 μm.

[0076] The image-recording layer may be present in any amount which iseffective for the intended purpose. In general, good results areobtained when it is present in an amount of from about 2 to about 46g/m², preferably from about 6 to about 16 g/m², which corresponds to adry thickness of about 2 to about 42 μm, preferably about 6 to about 15μm.

[0077] The following examples are provided to illustrate the invention.

EXAMPLES

[0078] Synthesis of Colorant A Composition

[0079] Colorant A Composition was prepared from Copper (II)phthalocyanine 4,4′,4″,4′″-tetrasulfonic acid or its salts which wasmade according to JP00303009A.

[0080] Copper (II) phthalocyanine 4,4′,4″,4′″-tetrasulfonic acid (5 g)was suspended in sulfolane (100 ml), and thionyl chloride (100 ml) wasadded all at once followed by dimethylformamide (0.5 g). The mixture wasrefluxed for 48 hours, insolubles were filtered off and discarded, andexcess thionyl chloride was evaporated using a rotary evaporator.Diethanolamine (19 g) was then added while stirring and keeping thereaction temperature between 45 and 55° C. After stirring for 2 hours at55° C., diisopropyl ether (250 ml) was added to the resulting reactionmixture, and stirring was continued for 2 hours at ambient temperature.The colorless layer was decanted, and isopropyl alcohol (250 ml) wasadded. The mixture was stirred for 6 hrs at ambient temperature. Theprecipitate was filtered, washed with ethanol (200 ml) at 70° C. anddried in vacuo to give Colorant A Composition (4.3 g).

[0081] Synthesis of Colorant B Composition

[0082] Colorant B Composition was made the same as Colorant AComposition except Direct Blue 199, sulfonated copper phthalocyaninedye, obtained by freeze drying an aqueous solution available fromTricon, Inc. was used as the starting material.

[0083] Synthesis of Colorant C Composition

[0084] Colorant C Composition was made the same as Colorant AComposition except Nickel (II) phthalocyanine 4,4′,4″,4′″-tetrasulfonicacid was used as the starting material.

[0085] Synthesis of Colorant D Composition

[0086] 10 g of quinacridone (PV Fast Red ESB available from ClariantCorporation) was added in portions to 100 g of chlorosulfonic acid at<15° C. under a nitrogen atmosphere. The resulting purple solution washeated in an 80° C. oil bath for 3 hours, 5 mL thionyl chloride wasadded and heating continued at 80° C. for 2 more hours. The reactionmixture was transferred to a rotary evaporator and the volatiles removedat 50° C. The residue was cooled to room temperature and slowly added to400 g of ice with good mixing. The resulting red-orange solid wascollected by filtration and rinsed with cold water. The solid cake wasallowed to air-dry overnight, ground with a mortar and pestle, slurriedwith acetone and filtered to yield crude quinacridone bis-sulfonylchloride.

[0087] 10 g of the crude sulfonyl chloride from above was added inportions to a solution of 9.2 g diethanolamine in 100 mL DMF at <15° C.The resulting suspension was stirred at ambient temperature for 3 hoursand added to 400 mL methanol with stirring. The solid product wascollected by filtration and rinsed with methanol. The methanol-DMFsoluble fraction is mainly quinacridone bis-sulfonate. The crude productwas further purified by re-suspension in 50 mL warm DMF, dilution with100 mL methanol, cooling to room temperature and filtration. The solidwas ground with a mortar and pestle and slurried in acetonitrile toyield 10.2 g of a red-orange solid. Mass spectral and HPLC analysesindicated that the product was predominately Colorant 37, with traces ofbis-sulfonate and bis-(diethanolsulfonamide) products.

[0088] Receiving Elements

[0089] The following commercially-available receiving elements with aporous image-receiving layer were used:

[0090] Receiving Element 1

[0091] Kodak Professional Inkjet Products, Instant-Dry PhotographicGlossy Paper, CAT 8987752.

[0092] Receiving Element 2

[0093] Konica Photo Quality Ink Jet Paper QP, No: KJP-LT-GH-15-QP PI.

[0094] Ink Preparation

[0095] Inks were formulated to give a maximum density of approximately1.2-1.4, when printed onto the above receiving elements using a LexmarkZ51®, thermal head printer. The concentration of colorants in theformulation could be adjusted to achieve other levels of coverage. Inksfor printing via a Piezo head using a Mutoh 4100® wide format printerare described hereinafter.

[0096] Thermal Cyan Ink Formulations

[0097] 1) Ink from Colorant C Composition

[0098] Colorant C Composition (0.338 g) was stirred overnight with water(2 g) and a solution (5 g) containing glycerol (37% by weight),diethylene glycol (12.5%), and butoxytriglycol (14%) in water (to 100%).Once no solids remained, a further quantity of water (2.66 g) was addedto generate 10 g of ink. This ink was filtered through a 0.45 μmpolytetrafluoroethylene filter pad then loaded into a Lexmark cartridgeto be printed using a Lexmark Z51® printer.

[0099] 2) Ink from Colorant C Composition/Direct Blue 199 (Tricon, Inc.Green Shade 1837-P) Mixture

[0100] 10 g sample of ink was prepared similar to 1) from Colorant CComposition (0.169 g) and DB-199 concentrate (1.171 g).

[0101] 3) Ink from Colorant A Composition

[0102] 10 g sample of ink was prepared similar to 1) from Colorant AComposition (0.21 g) to print to a maximum density of approximately 1.0.

[0103] 4) Ink from Colorant B Composition

[0104] 10 g sample of ink was prepared similar to 1) from Colorant BComposition (0.21 g) to print to a maximum density of approximately 1.0.

[0105] C-1 Comparison Ink from Direct Blue 199 (Tricon, Inc. Green Shade1837-P)

[0106] 10 g sample of ink was prepared similar to 1) from the dyeaqueous DB-199 concentrate (2.342 g).

[0107] C-2 Comparison Ink from Avecia Pro-Jet™ Fast Cyan 2 (Liquid)

[0108]10 g sample of ink was prepared similar to 1) from the dye aqueousconcentrate (1.523 g).

[0109] C-3 Ink from Bayer Bayscript Cyan BA™

[0110]10 g sample of ink was prepared similar to 1) from the dye aqueousconcentrate (0.9 g).

[0111] Piezo Light Cyan Ink Formulations.

[0112] These were prepared to have viscosity in the range of 2.8-3.0 cpand were adjusted to a pH of about 8.1.

[0113] 5) Ink from Colorant A Composition

[0114] For 80 g of ink, Colorant A Composition (1.6 g) was stirredovernight with a mixture of glycerol (3.44 g), diethylene glycol (6.8g), butoxytriglycol (6.4 g), 2-pyrrolidinone (3.44 g) and water (58.32g). The pH of the mixture was measured and adjusted to pH=8.18 bycareful addition of a dilute solution of triethanolamine. The mixturewas filtered through a 0.45 μm polytetrafluoroethylene filter pad thenloaded ready for printing using a Mutoh 4100®, wide format printer.

[0115] 6) Ink from Colorant B Composition

[0116] This ink was prepared the same as 5) above except using the dye(1.6 g), glycerol (8.0 g), diethylene glycol (8.0 g), butoxytriglycol(6.4 g), and water (56.0 g).

[0117] C-4 Comparison Ink from Avecia Pro-Jet™ Fast Cyan 2 (Liquid)

[0118] This ink was prepared the same as 5) above except using the dyeconcentrate (6% dye, 16 g), glycerol (9.4 g), diethylene glycol (10.8g), butoxytriglycol (5.6 g), and water (38.2 g).

[0119] Thermal Magenta Ink Formulations

[0120] 7) Ink from Colorant D Composition

[0121] Colorant D Composition (0.817 g) was stirred overnight with water(2 g) and a solution (5 g) containing tetraethylene glycol (30% byweight), 2-pyrrolidinone (16%), and 1,2-hexanediol (14%) in water (to100%). A further quantity of water (1.68 g) and triethanolamine (0.5 g)were added to generate 10 g of ink. This ink was filtered through a 0.45μm polytetrafluoroethylene filter pad then loaded into a Lexmarkcartridge to be printed using a Lexmark Z51® printer.

[0122] C-5 Comparison Ink from Ex. 2 of U.S. Pat. No. 6,152,968(Structure Shown Below)

[0123] 10 g sample of ink was prepared similar to 7) from this colorant(0.937 g), water (2 g+1.56 g), triethanolamine (0.5 g) and a solution (5g) containing tetraethylene glycol (30% by weight), 2-pyrrolidinone(16%), and 1,2-hexanediol (14%) in water (to 100%).

[0124] Evaluation

[0125] Various test targets were printed, using two ink jet receivingelements, to allow examination of several density level patches (approx10 mm square) ranging from 100% dot coverage to less than 25% dotcoverage. Printed samples were then subjected to image stability testingunder a variety of conditions. These tests are described below.Typically the Status A red (for cyans) or green (for magentas)reflection density of the 100% and 75% dot coverage (or other) patcheson a fresh sample were measured using an X-Rite 820® densitometer,corrected for the color of the receiver, and recorded. That sample wassubjected to a test described below and re-read. The percentage of dyedensity remaining relative to the fresh sample was calculated, to give ameasure of colorant fastness on a particular receiver. These data aregiven in the Tables below.

[0126] Atmospheric Contaminants Test

[0127] Printed samples were mounted in a darkened chamber maintained atroom temperature, with a constant atmosphere containing 5 ppm of Ozone,and at a relative humidity of approximately 50%. The samples wereremoved after a time period of 24 hours. The results are shown in theTables below.

[0128] High Intensity Simulated Daylight Fading (HID) Test

[0129] Samples were mounted in a temperature and humidity controlledchamber where they were subjected to 50 Klux light exposure from afiltered xenon light source, designed to match the spectralcharacteristics of daylight, for a period of two weeks. The results areshown in the Tables below.

[0130] Printing of Test Images Using a Thermal Head

[0131] To print using a thermal head, the above prepared inks 1-4, 7 andC-1 to C-3, C-5 were placed into empty Lexmark ink cartridges, No.15MO120, and fitted into the ink station of a Lexmark Z51® printer. Theywere printed on to receiving elements 1 and 2 with the resultssummarized in Tables 2 to 4. TABLE 2 Atmospheric Contaminants HID, LightFastness Test Test (% retained) (% retained) Receiving 100% dot 75% dot100% dot 75% dot Ink Element coverage coverage coverage coverage C-1 130% 33% 86% 84% C-1 2 29% 32% 79% 75% 1 1 98% 95% 104% 101% 1 2 97% 97%99% 102% 2 1 77% 76% 94% 93% 2 2 72% 70% 94% 89%

[0132] The above results show that on either receiving element, theinventive ink compositions 1 and 2 show considerable improvements in thelight fastness and ozone fastness over that of the comparison inkcomposition. TABLE 3 Atmospheric Contaminants HID, Light Fastness TestTest (% retained) (% retained) Receiving 100% dot 75% dot 100% dot 75%dot Ink Element coverage coverage coverage coverage C-1 1 21% 23% 75%75% C-1 2 28% 29% 70% 65% C-2 1 28% 29% 69% 66% C-2 2 24% 28% 56% 49%C-3 1 45% 47% 84% 82% C-3 2 46% 47% 82% 79% 3 1 92% 89% 98% 96% 3 2 94%94% 100% 97% 4 1 91% 93% 99% 99% 4 2 93% 93% 98% 98%

[0133] The above results show that on either receiving element theinventive ink compositions 3 and 4 show considerable improvements in thelight fastness and ozone fastness over that of the comparison inkcompositions C-1, C-2 and C-3. TABLE 4 Atmospheric Contaminants HID,Light Fastness Test Test (% retained) (% retained) Receiving 100% dot75% dot 100% dot 75% dot Ink Element coverage coverage coverage coverageC-5 1 16% 17% 12% 15% C-5 2 21% 23% 16% 20% 7  1 90% 91% 80% 81% 7  288% 88% 95% 94% 2^(nd) Experiment C-5 1 16% 20% 18% 25% C-5 2 19% 28%23% 26% 7* 1 92% 93% 87% 88% 7* 2 95% 94% 87% 87%

[0134] The above results show that on either receiving element, theinventive ink composition 7, with or without triethanolamine, showsconsiderable improvement in stability to fading by both light and byatmospheric contaminants such as ozone over that of the comparison inkcomposition C-5.

[0135] Printing of Test Images Using a Piezo Head

[0136] To print using a Piezo head, inks C-4, 5 and 6 were placed inempty ink sachets, the remaining air was removed by bleeding and thesachets were fitted into a bay of the Mutoh 4100® printer. The followingresults were obtained: TABLE 5 Atmospheric Contaminants HID, LightFastness Test Test (% retained) (% retained) At At Receiving Maximum AtMaximum Ink Element Density Density = 1 Density At Density = 1 C-4 1 24%23% 75% 71% C-4 2 25% 25% 55% 55% 5 1 97% 92% 98% 99% 5 2 99% 98% 99%99% 6 1 88% 91% 97% 97% 6 2 88% 88% 95% 94%

[0137] The above results show that the inventive inks are better thanthe comparison ink for both light and ozone fastness.

[0138] Physical Nature of the Inventive Colorants in the Inks byMicroscopy

[0139] Four thermal ink samples (1-3 and C-1 were analyzed bytransmission electron microscopy (TEM) in a JEM-2000FX® operating ateither 200 or 100 kV accelerating voltage, and by optical microscopy(OM) at magnifications up to 1000× in an Olympus BX30® microscope. Fordirect microscopy examination of ink formulations, suitable samples wereprepared by spreading a small drop of the ink onto a carbon filmsupported on 200 mesh aluminum TEM grid (SPI Inc., West Chester, Pa.19381). The complementary observation of ink written onto the receivingelements set forth in the invention was performed using suitablecross-sectioned samples, prepared by cryomicrotomy in a ReichertUltracut S® microtome, equipped with a Reichert FCS® cryo-temperatureattachment and a diamond knife. Small area composition analysis wascarried out with Energy Dispersive Spectroscopy (EDS) using a focusedelectron beam, ˜20 nm in diameter. The method used follows the standardanalysis technique as outlined in published books (e.g. see “Principlesof Analytical Electron Microscopy”, Chapters 4 and 5, Edit. D. C. Joy,A. D. Romig, and J. I. Goldstein, Plenum Press, New York, 1989).

[0140] For ink 1, TEM analysis revealed the ink contained a non-uniformmicrostructure consisting mostly of spherically shaped islands, andoccasionally, irregularly shaped facetted particulates. The formerexhibited uniform contrast in the TEM, indicating that they areamorphous solids, and were found to have the range approximately between10 and 20 nm. Further, these islands are found to comprise agglomeratesof amorphous colorant solids, and as such are larger than the individualcolorant particles. The facetted particulates showed black and whitecontrast indicating crystalline characteristics, and they ranged from 40to 100 nm. Both the islands and particulates were found to contain Niand S by EDS, consistent with the colorant composition. For ink writtenon receiving element 1, TEM observations revealed a distinct layer ofcolorant deposited at the surface. At 100% dot coverage using theLexmark Z51® printer, this layer thickness was approximately 0.1 μm±0.05μm. In a complimentary fashion, optical microscopy showed that thecolorant had not significantly penetrated into the receiving elements,but instead is confined as a thin layer at the surface. Taken together,the microstructure and composition data indicate that the ink contains ananoparticulate dispersion of amorphous and crystalline colorants. Thesecharacteristics are distinctly different than those found for thecomparison ink composition C-1.

[0141] For ink 2, TEM results similar to those of 1 were found. The inkdispersion consisted mostly of spherically shaped islands, andoccasionally irregularly shaped facetted particulates. The formerexhibited uniform contrast in the TEM, indicating their amorphousnature, and were found to be approximately 10-20 nm in size. Further,these islands are found to comprise agglomerates of amorphous colorantsolids, and as such are larger than the individual colorant particles.The latter showed black and white contrast, indicating their crystallinematrix, and ranged in size from approximately 40 to 100 nm. Both theislands and the particulates were found to contain Ni, Cu and S, asanalyzed by EDS, consistent with the colorant composition. For inkwritten on receiving element 1, TEM observations revealed a distinctlayer of colorant deposited at the surface. At 100% dot coverage usingthe Lexmark Z51® printer, this layer thickness was approximately 0.1μm+0.05 μm. In a complimentary fashion, optical microscopy showed thatthe colorant had not significantly penetrated into the receivingelements, but instead is confined as a thin layer at the surface. Takentogether, the microstructure and composition data indicate that the inkcontains a nanoparticulate dispersion of amorphous and crystallinecolorants. These characteristics are distinctly different than thosefound for the comparison ink composition C-1.

[0142] For ink 3, TEM analysis revealed the ink to exhibitmicrostructural characteristics similar to those of 1 and 2. Itconsisted of spherically shaped solid islands, and irregularly shapedfacetted particulates. The former exhibited uniform contrast in the TEM,indicative of its amorphous matrix, and was found to have sizes rangingfrom 10-20 nm. Further, these islands are found to comprise agglomeratesof amorphous colorant solids, and as such are larger than the individualcolorant particles. The latter showed black and white contrast,indicative of its crystalline matrix, and they ranged from approximately40 to 100 nm. Both the islands and the particulates were found tocontain Cu and S, as analyzed by EDS, consistent with its colorantcomposition. For ink written on receiving element 1, TEM observationsrevealed a distinct layer of colorant deposited at the surface. At 100%dot coverage using the Lexmark Z51® printer, this layer thickness wasapproximately 0.1 μm±0.05 μm. In a complimentary fashion, opticalmicroscopy showed that the colorant had not significantly penetratedinto the receiving elements, but instead is confined as a thin layer atthe surface. Taken together, the microstructure and composition dataindicate that the ink contains a nanoparticulate dispersion of amorphousand crystalline colorants. These characteristics are distinctlydifferent than those found for the comparison ink composition C-1.

[0143] For ink C-1, when it was spread out and dried on the carbon film,TEM data showed the ink was uniform in morphology, with no discerniblemicrostructure feature. Under the optical microscope, this dried inkexhibited a cyan color and formed a uniform film. When printed onreceiving elements 1 and 2, cross-section TEM data revealed no soliddeposit at the surface. Cross-section OM observations showed thiscolorant had significantly penetrated into the receiving elements. Theseobservations are consistent with the characteristics of solubledye-based inks that can penetrate into the receiving elements after theink deposition process.

[0144] Physical Nature of the Inventive Colorants in the Inks byCentrifugation

[0145] Ink samples 3, 4, C-1 and C-3 were used to fill centrifuge tubesand were subjected to centrifugation for 24 h, using a Beckman UltraCentrifuge® with conditions of 60,000 rpm at 20° C. A 100 μL sample wastaken from the top 5 mm of the centrifuge tube, before and aftercentrifugation. These were diluted with deionized water using the samedilution factor such that the range of absorbance seen when the visiblespectra of the samples taken before centrifugation was within the rangeof the spectrometer. For each sample, the spectral absorbance maximumbetween 400 nm and 700 nm was recorded before centrifugation (D₁) andcompared to the absorbance at that wavelength after centrifugation (D₂).The ratio of these values D₂/D₁ expressed as a percentage is anindicator of the proportion by weight of the colorant in the ink thatexists in solution. The value 100−(D₂/D₁) % is then an indicator of theproportion by weight of the colorant that is in particulate form. Theseresults are given in Table 6 below. TABLE 6 Colorant Ink 100-(D₂/D₁) % A3 86% B 4 83% DB199 C-1 34% Bayscript Cyan BA ™ C-3 50%

[0146] A similar experiment was performed using inventive colorantcomposition 7 (made from colorant D, with no triethanolamine) andcomparison C-5. The results are shown in Table 7 below. TABLE 7 ColorantInk 100-(D₂/D₁) % D 7* 75% Ex. 2 of U.S. C-5 21% 6,152,968

[0147] The above results show that in the invention ink compositions,the colorants exist predominantly as particles that are capable ofsedimentation when centrifuged, which is not the case for the comparisonink compositions.

[0148] Although the invention has been described in detail withreference to certain preferred embodiments for the purpose ofillustration, it is to be understood that variations and modificationscan be made by those skilled in the art without departing from thespirit and scope of the invention.

What is claimed is:
 1. An ink jet printing process comprising the stepsof: A) providing an ink jet printer that is responsive to digital datasignals; B) loading said printer with ink jet recording elementscomprising a support having thereon an image-receiving layer; C) loadingsaid printer with an ink jet ink composition comprising water, humectantand a self-assembling colorant that is capable of spontaneously forminga nanoparticulate dispersion without any prior physical attrition orsurface modification, said colorant having the formula:(A)_(m)-Q-(Z)_(n) wherein: Q represents a chromophore; each Aindependently represents an organic or inorganic group capable ofhydrogen bonding or other non-covalent bonding; each Z independentlyrepresents an organic or inorganic group capable of electrostaticbonding; and m and n each independently represents an integer from 0 to10; with the proviso that n+m is at least 1; and with the furtherproviso that at least about 50 wt. % of the colorant is present in thecomposition as particles; and D) printing on the image-receiving layerusing said ink jet ink in response to said digital data signals.
 2. Theprocess of claim 1 wherein said Q represents a colorant selected fromthe class consisting of anthraquinone, naphthoquinone, quinacridone,quinophthalone, indigo, thioindigo, perylene, dioxazine,1,4-diketopyrrolopyrrole, anthrapyridine, anthrapyrimidine,anthanthrone, flavanthrone, indanthrone, isoindoline, isoindolinone,perinone, pyranthrone, porphyrin, and azo chromophores.
 3. The processof claim 1 wherein each said A independently represents sulfonate,sulfinate, phosphonate, carboxylate, ammonium, substituted ammonium,pyridinium, amidinium or guanidinium.
 4. The process of claim 1 whereinsaid Z represents hydroxy, a sugar residue, a polyoxyalkylene group, asulfamoyl or carbamoyl group and its mono- and di-substitutedderivatives, a heterocyclic group or an alkylsulfonyl group.
 5. Theprocess of claim 1 wherein said colorant is present in an amount of fromabout 0.2 to about 10 wt. %, said humectant is present in an amount offrom about 5 to about 70 wt. %, and the balance is water.
 6. The processof claim 1 which also includes a water-soluble dye.
 7. The process ofclaim 1 wherein said particles are less than about 0.3 μm in size. 8.The process of claim 1 wherein said particles are less than about 0.1 μmin size.
 9. The process of claim 1 wherein said colorant has theformula:

wherein: each R₁ independently represents an alkyl group of from 1 toabout 6 carbon atoms, an alkoxy group of from 1 to about 6 carbon atoms,an alkoxycarbonyl group of from 1 to about 6 carbon atoms, halogen,cyano, nitro, carbamoyl, alkylsulfonyl, an alkylcarbamoyl group of from1 to about 6 carbon atoms or a dialkylcarbamoyl group of from 1 to about6 carbon atoms; R₂ and R₃ each independently represents H or an alkylgroup of from 1 to about 6 carbon atoms, optionally substituted with oneor more groups chosen from hydroxy, amino, dialkylamino, alkoxy,halogen, nitro, cyano, alkoxycabonyl and acyloxy; R₂ and R₃ may also bepart of a 5- to 7-membered heterocyclic ring; x represents an integerfrom 0 to 4; and Y represents hydrogen, alkali metal or an organiccation.
 10. The process of claim 1 wherein said support is paper,resin-coated paper or a plastic.
 11. The process of claim 1 wherein saidimage-receiving layer comprises interconnecting pores.
 12. The processof claim 11 wherein said image-receiving layer comprises from about 20%to about 95% inorganic particles and from about 5% to about 80% of apolymeric binder.
 13. The process of claim 11 wherein saidimage-receiving layer comprises organic particles.
 14. The process ofclaim 11 wherein said image-receiving layer comprises a polymericopen-pore membrane.
 15. The process of claim 12 wherein said inorganicparticles comprise silica, alumina, titanium dioxide, clay, calciumcarbonate, barium sulfate or zinc oxide.
 16. The process of claim 12wherein said polymeric binder is gelatin, poly(vinyl alcohol),poly(vinyl pyrrolidinone) or poly(vinyl acetate) or copolymers thereof.